A D-7 will weigh down to .1 gr., or zero actually, same as any other reloading scale.
+1 on what wncchester said,I've had and use a set of Lyman D-7 scales for 20+ years.
For the D-7
On the right side it will measure up to 5 full grs. in 1/10th increments with each move of the small counterbalance. On the left side it measures in 5 gr. increments with each move of the larger counterbalance.
After zeroing the scale,If you want to weight out 6 grs. set the left adjustment on the first notch which is 5 grs. and the right notch on 1 which is one gr. for a total of 6 grs.
If you want to weigh a charge of say 10.2 grs. set the left adjustment on the second notch which is 10 grs. and the right adjustment on the second notch form the zero position which is 2/10 tenths.
Anything under 5.0 grs. just put the left setting on zero and use the right side. Anything over 5.0 grs. and you have to use both.